Plasma heating in ITER will require Neutral Beam Injectors (NBI) systems having unprecedented performances (16.5 MW beam power, up to 1 MeV specific energy and 1 hour continuous operation)This demand fostered an intense worldwide R&D effort on negative ion sources and accelerators, which are considered the most suitable to the purpose of producing high-power neutral beam
. A full scale prototype Injector will be tested and optimized in the Neutral Beam Test Facility at the CNR Research Area in Padova (Italy) so as to guarantee a stable and reliable operation of the ITER injector. The key component of the system is the beam source whose performance is strictly dependent on a deep understanding of the non-linear mechanisms behind the generation and acceleration of negative ions.Tacklingand solving the key issues emerging from the R&D requires competences coming from plasma physics, chemistry and accelerator physics and technology and shows the potential of establishing new (and sometimes unexpected) bridges towards other disciplines.
This contribution will present the status and the perspectives of the beam source R&D focusing on two aspects: a) the pivotal role of the status of the surfaces for the negative ions generation and for the high voltage holding and b) the emerging complex network of mechanisms underlying the negative ion generation and extractions which has been found suited to interconnections with astrophysics and to modern approaches to the controllability of complex systems. Finally an alternative innovative concept for a new generation of negative ion sources will be mentioned as an example of how well-established technologies from other fields, in this case from space propulsion, can be applied to improve efficiency and reduce complexity of the source.